Setup Travis CI integration

Trying again with a PPA for glfw3-dev

.travis.yml

@@ -1,14 +1,13 @@
 language: cpp
 
 os:
-  - osx
+  - linux
-osx_image: xcode61
 
 compiler:
   - gcc
 
 before_install:
-  - if [ $TRAVIS_OS_NAME == linux ]; then sudo apt-get update -qq && sudo apt-get install -y --no-install-recommends libglfw3-dev libglew-dev; fi
+  - if [ $TRAVIS_OS_NAME == linux ]; then sudo add-apt-repository ppa:keithw/glfw3 && sudo apt-get update -qq && sudo apt-get install -y --no-install-recommends libglfw3-dev libglew-dev; fi
   - if [ $TRAVIS_OS_NAME == osx ]; then brew update && brew install glew && brew install glfw3; fi
 
 script: